commit 4d7c37e12ef4ceb6903dd76ee700beb99fbf5f8e
author Kevin O'Connor <kevin@koconnor.net> Fri Dec 26 23:50:17 2008 -0500
committer Kevin O'Connor <kevin@koconnor.net> Fri Dec 26 23:50:17 2008 -0500
tree 775ea50649f399752e929bd7cdcdc14e42a548c6
parent 4735877249b30502e4c816bf1dc1a2c0e16be68e

Support a relocatable ebda segment.

Some option roms will try to relocate the ebda.
Also fix an apparent typo in the assignment of ivecs[0x46].

src/post.c

diff --git a/src/post.c b/src/post.c
index f55d53d..5951644 100644
--- a/src/post.c
+++ b/src/post.c
@@ -19,7 +19,6 @@
 #include "bregs.h" // struct bregs
 
 #define bda ((struct bios_data_area_s *)MAKE_FARPTR(SEG_BDA, 0))
-#define ebda ((struct extended_bios_data_area_s *)MAKE_FARPTR(SEG_EBDA, 0))
 
 void
 __set_irq(int vector, void *loc)
@@ -39,8 +38,6 @@
     dprintf(3, "init bda\n");
     memset(bda, 0, sizeof(*bda));
 
-    SET_BDA(mem_size_kb, BASE_MEM_IN_K);
-
     // Initialize all vectors to a dummy handler.
     int i;
     for (i=0; i<256; i++)
@@ -78,14 +75,19 @@
 static void
 init_ebda()
 {
+    int esize = DIV_ROUND_UP(sizeof(struct extended_bios_data_area_s), 1024);
+    SET_BDA(mem_size_kb, 640 - esize);
+    u16 eseg = FARPTR_TO_SEG((640 - esize) * 1024);
+    SET_BDA(ebda_seg, eseg);
+
+    struct extended_bios_data_area_s *ebda = get_ebda_ptr();
     memset(ebda, 0, sizeof(*ebda));
-    ebda->size = EBDA_SIZE;
-    SET_BDA(ebda_seg, SEG_EBDA);
-    SET_BDA(ivecs[0x41].seg, SEG_EBDA);
+    ebda->size = esize;
+    SET_BDA(ivecs[0x41].seg, eseg);
     SET_BDA(ivecs[0x41].offset
             , offsetof(struct extended_bios_data_area_s, fdpt[0]));
-    SET_BDA(ivecs[0x46].seg, SEG_EBDA);
-    SET_BDA(ivecs[0x41].offset
+    SET_BDA(ivecs[0x46].seg, eseg);
+    SET_BDA(ivecs[0x46].offset
             , offsetof(struct extended_bios_data_area_s, fdpt[1]));
 }
 
@@ -123,7 +125,8 @@
     add_e820(0xa0000, 0x50000, E820_HOLE);
 
     // Mark known areas as reserved.
-    add_e820((u32)MAKE_FARPTR(SEG_EBDA, 0), EBDA_SIZE * 1024, E820_RESERVED);
+    add_e820((u32)MAKE_FARPTR(GET_BDA(ebda_seg), 0), GET_EBDA(size) * 1024
+             , E820_RESERVED);
     add_e820(BUILD_BIOS_ADDR, BUILD_BIOS_SIZE, E820_RESERVED);
 
     dprintf(1, "ram_size=0x%08x\n", GET_EBDA(ram_size));
@@ -153,6 +156,7 @@
     dprintf(3, "init boot device ordering\n");
 
     // Floppy drive
+    struct extended_bios_data_area_s *ebda = get_ebda_ptr();
     struct ipl_entry_s *ip = &ebda->ipl.table[0];
     ip->type = IPL_TYPE_FLOPPY;
     ip++;